On June 29, 2012 a derecho surged east-southeast from the Ohio Valley across the Mid-Atlantic region causing widespread wind damage resulting in the loss of 4,000,000 people without power. Yesterday a similarly intense derecho moved rapidly across the Midwest U.S. knocking out power to over 500,000 people.

Steady pulses of African dust continue to emit westward in the North Atlantic tropics suppressing tropics cyclone activity. However, the relative humidity/available moisture at mid-level atmosphere is increasing. The mid-level atmosphere increased humidity is very supportive of the tropics starting to percolate.

A La Nina Watch remains in-place for 1-3 months from now and there are some signs of La Nina diagnostics returning. Last week the Nino34 SSTA lowered to -0.8C. The SOI in July was in the positive phase and the subsurface cool water near the Dateline is new and expanding. Despite the loss of the APR/MAY cool subsurface there remains a chance of La Nina onset by early in quarter 4 of 2020.